May 2021 Gate Project Update for Lake Houston Dam

In its March 10th board meeting, the Coastal Water Authority (CWA) accepted the recommendation of a preliminary engineering report to add one thousand feet of crest gates to the uncontrolled spillway portion the Lake Houston Dam. The additional release capacity would let operators shed water faster before, during or after major storms to reduce the risk of flooding.

At the March meeting, directors also approved $4.4 million to begin Phase II of the project. Phase II calls for Black & Veatch to proceed to final engineering of the gates and a coffer dam to protect the work area during construction.

Read the minutes of the March board meeting here. The discussion of the gates starts on page 4 under Item B.

This morning, at its May board meeting, directors received an update on the progress of Phase II work to date and plans for the remainder of the project.

Start of Phase II Engineering Approved in March

In the March meeting, CWA approved funds to begin Phase 2 of the engineering which includes the final design of the selected alternative by Black & Veatch. The selected alternative was “crest gates” constructed on the uncontrolled spillway portion of the dam on its west side. (See below.)

Dam operators can raise or lower crest gates from a bottom hinge, much like the lid on a piano. When in the up position, gates hold water back. When lowered, they release water.

During Harvey, the peak flow over the spillway was five times the average flow over Niagra Falls. A wall of water 11 feet tall cascaded over the spillway above. Enough to fill NRG stadium in 3.5 minutes.

Scope of Phase II Design Work

Also in March, CWA and Black & Veatch completed negotiation of the scope and fee for the final design. The key deliverables during Phase II will include:

• Plans to modify the spillway to support the 1,000 linear feet of crest gates (in five 200-foot long sections)
• Design of the cofferdam system to protect the work areas during construction
• Preparation of a new gate operations plan for CWA Lake Houston Dam operators.

Director Douglas Walker moved to authorize the Executive Director to issue a contract amendment with Black & Veatch Inc. in the amount of $4,465,727.00 for “Phase 2 – Final Design of the Lake Houston Dam Spillway Improvement Project.” Director Giti Zarinkelk seconded the motion. The Motion carried unanimously.

May Update

In the May board meeting this morning, directors received an update on Phase II work to date and plans.

In April, the design team held a number of workshops and coordination meetings.

Black & Veatch also completed three weeks of field surveying of the existing spillway; that’s why CWA temporarily lowered Lake Houston during that period.

In other news, for next steps CWA will:

• Submit the permit application to the US Army Corps of Engineers by the end of May.
• Support City of Houston in a public outreach meeting scheduled for June 17. The public outreach meeting will coincide with the public comment period for the permit application. CWA expects permitting to take nine months, i.e., through March of 2022.
• Complete final design by the end of September 2022.

Next Steps

Does all this mean construction is assured? No. The Army Corps could reject the permit or FEMA could find some fault with the plans. But at least it shows progress. If all plans and permits are approved, construction dollars have already been committed by FEMA. Originally, construction was supposed to have been completed within three years from April 8, 2020. That now looks unlikely unless the City can obtain a deadline extension from FEMA..

Posted by Bob Rehak on 5/12/2021

1352 Days after Hurricane Harvey